1. Field of the Invention
The present invention relates to an elevator having a compensating cable and, more particularly, to a dampening device for a compensating cable operably engaged with an elevator car, capable of dampening oscillation of the compensating cable and indicating an abnormal condition thereof, and associated system and method.
2. Description of Related Art
An elevator car installation typically uses a compensating cable arrangement, as will be appreciated by one skilled in the art. Such a compensating cable is generally very flexible and can be hung at very long lengths in an elevator hoistway. Because the compensating cable is attached to the elevator car and a counterweight, which move vertically and opposite each other, the cable is susceptible to oscillations and/or swaying during operation of the elevator. The oscillations of the cable are typically of the greatest magnitude and the most evident in the pit area at the bottom of the elevator hoistway, which is where the cable forms a loop. The oscillations of the cable may pose a problem in the pit when the cable moves and sways near equipment therein. More particularly, the oscillations and/or swaying of the cable can cause the loop to become entangled with the pit equipment or to possibly fall outside the influence of one or more dampening devices intended to dampen the motion of the cable. Thus, during operation, the compensating cable may be at risk of becoming entangled and/or overloaded, and thereby possibly raising operational and safety concerns.
One compensating cable installation method requires a safety loop to be incorporated into the compensating cable. The safety loop may be, for example, located underneath the elevator car where a loop of the compensating cable is supported from the car with a deformable S-hook. The S-hook functions as a mechanical safety link such that, should the compensating cable become entangled and/or overloaded, the S-hook yields and the slack or excess length of cable forming the loop is released from the elevator car. One intended effect of such a configuration is that the released excess cable will allow the cable to untangle itself, thereby reducing the risk of damage to the cable should it become severely overloaded. However, if the elevator car is moving downward and the cable happens to become entangled in the pit or with pit equipment, the portion of the cable underneath the counterweight will tend to become overloaded, while the portion of the cable underneath the car will be slack. As such, the safety loop may not work properly in that instance.
Thus, there exists a need for a dampening device for shallow elevator pits that will not transfer or apply torsion or other forces to the compensating cable, but is capable of dampening the sway of the cable resulting from centrifugal forces and oscillations during operation. Such a dampening device should be operable with different cable configurations, such as a round compensation cable or a flat compensation cable, should contain the cable loop in its proper position, and should properly guide the cable so as to prevent potential entanglements. The dampening device should desirably provide an alternative to or supplement for the compensating cable safety loop, by detecting an abnormal or unsafe compensating cable condition and, as a result, indicating the condition and/or stopping operation of the elevator before damage and/or injury occur. More particularly, such a device should be capable of signaling or warning of an unsafe compensation cable loop condition such as, for example, when the loop in the pit is hanging too low from suspension rope stretch or when the loop is too high due to entanglement of the cable.